1. Field of the Invention
The present invention relates to the field of image displaying techniques, and in particular to a panel display and a manufacturing method thereof, and a panel display device.
2. The Related Arts
Optical etching process is important to the manufacturing of a panel display device. The main steps comprise: thin film deposition→photo-resist coating→exposure→photo-resist lithography→thin film etching→photo-resist removal. Under normal circumstances, photo-resist lithography uses liquid lithography solution, and the thin film etching of metal (alloy) layer uses liquid etching solution for etching. Both are so called wet processes. In wet process, the thin film pattern on a substrate will affect local concentrations of an ingredient in the solution. That is, if the area of the photo-resist or the area of the metal (alloy) requires lithography is large, more ingredient will be consumed; on the other hand, if the area of the photo-resist or the area of the metal (alloy) requires lithography is small, less ingredient will be consumed.
The solution has a diffusion effect to maintain the same concentration everywhere in the solution. When differences exist in the thin film patterns on the substrate, the ingredient in the solution will diffuse from high concentration place to lower concentration place during the lithography or etching process, which leads to different lithography or etching result for a boundary area of the pattern and a center area of the pattern. This effect is referred to as loading effect.
The following takes a photo-resist lithography process of a pixel electrode layer of a liquid crystal panel as an example to explain the bad influence of the loading effect on an active area (AA) of the liquid crystal panel.
FIG. 1 shows a design of a pixel electrode layer of a known liquid crystal panel. The center of the panel is an active area 1, which has a small photo-resist area requiring lithography. The majority outside of the active area 1 is a vacant area 2, which has a large photo-resist area requiring lithography. By enlarging the view of the boundary area A′ of the active area 1 in FIG. 1, the inner side design is a normal pixel area 3, with a tidy ITO electrode array, and the outer side design is the vacant area (without ITO electrode array) 4. Because of the loading effect, the actual photo-resist lithography process is different from the idealistic design. The actual result is shown in FIG. 2. Similarly, by enlarging the view of the boundary area A′ of the active area 1 in FIG. 2, the boundary area 5 near the vacant area 4 will show pattern irregularity because of insufficient photo-resist lithography. The pixel irregularity becomes less towards the inner side, and the idealistic design appears at pixel area 3 that is located sufficiently inwards. The specific process that the loading effect affects photo-resist lithography is as follows: At the beginning of the lithography process, the active area 1 slowly consumes a small amount of lithography ingredient and the vacant area 2 rapidly consumes a large amount of lithography ingredient. The difference in concentration leads to lithography ingredient in the active area 1 diffusing towards vacant area 2. From the perspective of boundary area A′ of the active area 1, lithography solution concentration at the boundary area 5 shows obvious gradient decreasing; that is, the closer to vacant area, the lower the concentration of lithography solution. In a subsequent lithography process, lithography capability in the boundary area 5 decreases in a gradient manner, and the photo-resist lithography result is less for pixels closer to the vacant area 4. The loading effect lessens the photo-resist lithography result of the boundary area 5, which leads to pattern irregularity of etching process (mainly, unable to etch pattern or coarse etched pattern).
The pattern irregularity in the boundary area 5 will cause defective image display. Not only the luminance, view angle and response time are different from those of the normal pixel area 3, but also influences the charging and discharging characteristics of the normal pixel area 3. Hence, it is desirable to eliminate pattern irregularity.